Hybrid vehicles that rely on both internal combustion engines and direct current motors for power, and fuel cell vehicles that rely on electric motors driven by current from fuel cells, both have passenger compartments that are ventilated, heated and air conditioned, and have windshield glass that is defrosted. Automotive vehicles powered by internal combustion engines generate heat by combustion that is used to heat passenger compartments and defrost windshields, and use mechanical power transmitted from the engine by belts to compressors that drive air conditioning systems. Hybrid vehicles normally use only electric motors when cruising, but rely on internal combustion engines for acceleration, heat and air conditioning. It is desirable with hybrid vehicles to minimize operation of internal combustion engines. Fuel cell vehicles have no internal combustion engines, consequently air conditioning and heating can only be provided by electric current. In view of these considerations there is a need for heating, ventilating and air conditioning (HVAC) systems for hybrid and fuel cell vehicles, which operate at high efficiency and consume minimal space.